Uvod v termočlene in principe merjenja temperature

1, Uvod v termočlene
Termoelektrični zapisovalniki temperature pogosto uporabljajo termočlene kot elemente za merjenje temperature. Pogosto se uporabljajo za merjenje temperatur v območju od -200 stopinj do 1300 stopinj. V posebnih primerih lahko merijo visoke temperature do 2800 stopinj ali nizke temperature do 4K. Imajo značilnosti preproste strukture, nizkih stroškov, visoke natančnosti in širokega temperaturnega merilnega območja. Zaradi termočlenov, ki pretvarjajo temperaturo v električno energijo za zaznavanje, merjenje temperature, nadzor ter ojačanje in preoblikovanje temperaturnih signalov so zelo priročni, primerni za merjenje na dolge razdalje in avtomatsko krmiljenje. Pri kontaktni metodi merjenja temperature je uporaba termoelektričnih termometrov zelo razširjena.
2, princip merjenja temperature s termočlenom:
Definition: A sensor composed of two conductors that converts temperature into thermoelectric electromotive force is called a thermocouple. 2. Temperature measurement principle: The temperature measurement principle of a thermocouple is based on the thermoelectric effect. Two different materials of conductors A and B are connected in series to form a closed circuit. When the temperatures of contact 1 and 2 are different, if T>T0 (as shown in Figure 12-1 thermoelectric effect), a thermoelectric electromotive force will be generated in the circuit, and a certain amount of current will be generated in the circuit. This phenomenon is called thermoelectric effect. The thermoelectric electromotive force is denoted as EAB, and conductors A and B are called thermoelectric electrodes. Contact 1 is usually welded together and placed in a temperature measuring location to sense the measured temperature, hence it is called the measuring end (or working end, hot end). Contact 2 requires a constant temperature and is called the reference end (or cold end). 3. Thermoelectric effect: The closed circuit of a thermocouple composed of conductors A and B has two contact potentials, eAB (T) and eAB (T0), respectively, at the two junctions. Additionally, because T>T{{0}} obstaja potencial temperaturne razlike v prevodnikih A in B. Torej bi morala biti skupna termoelektrična elektromotorna sila EAB (T, T0) zaprtega kroga algebraična vsota kontaktno elektromotorno silo in elektromotorno silo temperaturne razlike, to je 4. Za izbrani termočlen, ko je referenčna temperatura konstantna, skupna termoelektrična elektromotorna sila postane funkcija ene vrednosti končne temperature meritve T, to je EAB ( T, T0)=f (T). To je osnovni princip merjenja temperature s termočleni. Pri dejanskem merjenju temperature je treba v zaprto zanko termočlena uvesti povezovalne žice in instrumente.